Chain-stitch-forming device for lock-stitch sewing machines

ABSTRACT

A chain-stitch-forming member is fitted into the loop of a lockstitch sewing machine in place of the usual bobbin case. The chain-stitch-forming insert member has a loop retaining projection for retaining a loop in cooperation with a needle of the machine and a cam mechanism between the loop taker and the projection to effect the prescribed movement of the projection to form chain-stitches as the machine operates.

United States Patent Chikao Yamashita Aichi-ken;

Koji Nishiyama, Osaka-shi, both of Japan 867,72 1

Oct. 20, 1969 Dec. 7, 1971 Brothers Kogyo Kabushiki Kaisha Mizuho-ku,Nagoya-shi, Japan [72] Inventors [21 App]. No. [22] Filed [45 Patented[73 Assignee [32] Priorities Sept. 1, 1969 [33] Japan Mar. 5, 1969,Japan, No. 44/ 16671; Oct. 21, 1968, Japan, No. 43/766611 [54]CIIAIN-STITCH-FORMING DEVICE FOR LOCK- STITCH SEWING MACHINES 13 Claims,18 Drawing Figs.

[52] U.S.Cl 112/168,

51 1111.0 005111/14 50 FieldoiSearch 112/168, 199,201,232,181,183

[56] References Cited UNITED STATES PATENTS 727,053 5/1903 Anthony112/168 3,173,390 3/1965 Bartosz 112/168 3,173,391 3/1965 Doerner112/168 3,253,560 5/1966 Ketterer et a1. 112/168 3,447,498 6/1969 Eguchi112/168 X Primary ExaminerH. Hampton Hunter Anorney-F1ynn & FrishaufABSTRACT: A chain-stitch-forming member is fitted into the loop of alock-stitch sewing machine in place of the usual bobbin case Thechain-stitch-forming insert member has a loop retaining projection forretaining a loop in cooperation with a needle of the machine and a cammechanism between the loop taker and the projection to effect theprescribed movement of the projection to form chain-stitches as themachine operates.

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PATENTEU DEE 7197i sum 120i 12 CIIAIN-S'IITCI-I-FORMING DEVICE FORLOCK-STITCH SEWING MACHINES The present invention relates to sewingmachines and more particularly to devices for converting a lock stitchsewing machine into a chain stitch sewing machine.

A sewing machine in common use is of a lock stitch type. It has beendesired that the machine be also capable of forming chain stitches ifrequired. While, to meet this demand, there have been employed varioustypes of chain stitch device, they are of complicated arrangement andfail to be easily fitted into the sewing machine.

With respect to the ordinary sewing machine having lock stitch forminginstrumentalities with a loop taker for performing lock stitches incooperation with a needle, the present invention consists in fitting achain stitch forming member into the loop taker in place of the ordinarybobbin case so as to permit always chain stitching of very goodconditions. According to the present invention, the chain stitch formingmember has the same shape and size and can be detachably fitted into theloop taker in the same manner as the ordinary bobbin case, so thatinterchange of the bobbin case for said chain stitch forming member orvice versa is very simple. Moreover, a sewing machine according to thepresent invention has exactly the same arrangement as the ordinary lockstitch type, except for said chain stitch forming, member, thus offeringgreat advantage in construction.

This invention can be more fully understood from the following detaileddescription when taken in connection with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view of an ordinary lock stitch sewing machinepermitting the use of a chain stitch forming device according to theinvention, wherein a frame is shown by two dot-dash lines and whichincludes a loop taker swingable around a horizontal axis extendingparallel with a direction of feeding of a work fabric;

FIGS. 2 to 7 jointly present a chain stitch forming device for fittingthe sewing machine shown in FIG. 1, according to an embodiment of theinvention; FIG. 2 is an elevation of an entire chain stitch formingdevice where a thread loop released from a loop taker is retainedby aloop retaining projection extended upwardly; FIG. 3' is a sectional viewon line 3-3 of the chain stitch forming device of FIG. 2; FIG. 4 is asimilar sectional view on line 3-3 of said device as taken from theopposite side of the device to that shown in FIG. 3 where the loopretaining projection is inclined in such direction as allows it to beremoved from the released loop; FIG. 5 is a plan view, with part brokenaway, of the device of FIG. 2 as taken from line 5-5 thereof; FIG. 6shows the perspective views of the constituent parts of the device ofFIG. 2; and FIG. 7 is a perspective view of a modification of the bridgemember of the device of FIG. 2;

FIGS. 8 to 11 jointly show a chain stitch forming device according toanother embodiment of the invention, said device being adapted for usein a lock stitch sewing machine wherein there is disposed a loop takerswingable around the horizontal axis normal to the direction in whichthe work fabric travels; FIG. 8 is a side view of said chain stitchdevice where there is retained by a loop retaining projection a threadloop released from the loop taker; FIG. 9 is a sectional view on line 99of the device of FIG. 8; FIG. 10 is a side view of said device similarto that of FIG. 8 where there is retained by the loop seizing beak ofthe loop taker a loop freshly formed by a result of the endwisereciprocation of the needle and FIG. 11 is a sectional view on line11-11 of the device of FIG. 10;

FIGS. 12 to 18 jointly illustrate a chain stitch forming deviceaccording toa third embodiment of the invention, which includes a looptaker rotatable around a horizontal axis extending parallel with adirection of feeding of a work fabric. FIG. 12 is an elevation of saiddevice where there is retained a loop released from the loop taker bythe upwardly truned loop retaining projection of a chain stitch formingmember of said device; FIG. 13 is a sectional view on line l3-13 of thedevice of FIG. 12; FIG. 14 is a plan view of the device of FIG. 12 astaken from line 1414; FIG. 15 is a sectional view of the device similarto that of FIG. 13 where there is released the loop; FIG. 16 is asectional view of a chain stitch forming member as taken from line 16-l6of the device of FIG. 13; FIG. 17 is a sectional view of said member ofFIG. 16 as taken from line 17-17 thereof; and FIG. 18 gives theperspective views of the dismembered parts of the member of FIG. 16.

A sewing machine shown in FIG. 1 is an ordinary lock stitch type, amachine frame 20 including a bed 21 from which rises a standard 22supporting a bracket arm 23 overhanging the bed. A main shaft 24journaled lengthwise in the bracket arm 23 drives all of the movingparts of the sewing machine and may be actuated by an electric motor(not shown), by a foot treadle or the like. A counterbalanced crank 25on the main shaft 24 is operatively connected by means of a connectingrod 26 to a needle bar 27 endwise slidable in a support 28 pivotallysecured as at 29 in the bracket arm and carrying at its lower extremityan eye-pointed needle 30. A needle thread takeup lever 31 is alsoactuated by said crank 25 and constrained by an anchor link 32 so as todraw tight and slacken the needle thread in timed relation with theendwise reciprocation of said needle 30. The path of the needle threadpasses from a supply (not shown) to a thread tension device 33 throughan eyelet 34 in the takeup lever 31, and then through appropriate guidessuch as the thread guide 35 on the needle bar 27 and to the needle eye.This needle thread control arrangement is typical of that which isrequired for lock stitch formation.

Below that part of the underside of the bed 21 which is disposed rightunder the needle 30 is provided a stitch forming or loop taker assembly36 for carrying out a sewing operation cooperated with said needle asshown in FIGS. 2 to 7. Reference 37 is a loop taker housing secured tothe frame in which an internal circular raceway 39 is defined by a coverring 38 consisting of the part of said housing and the inner surfacethereof. In the raceway 39 is formed a discontinuous peripheral bearingrib 40 and removably attached a loop taker 42 having a loop seizing beak41 at its end portion in which a ordinary bobbin case 43 may beaccommodated. The bobbin case is prevented from swinging with the looptaker by a recess 44 of said cover ring 38 as well known. Under the bedis provided a loop taker shaft 46 at the end of which is secured adriver 45 which causes the loop taker 42 to swing around the horizontalaxis thereof. Under the bed also is mounted a swing shaft 49 which isrotated by a crank rod 48 connected to a crank portion 47 of said mainshaft 24, the shaft 49 driving the loop taker shaft 46 through a set ofbevel gears 50, 51. Consequently, the needle 30 and loop taker 42 aredriven in time relation to seize a loop of a thread 52 carried on theeye of the needle 30 by the loop taker 42 during stroke of the needle 30downwardly through a needle aperture 53 of a needle plate 54 supportedby said bed 21 and the release of said seized loop from the loop taker42 during the succeeding upward stroke of the needle 30 in thisembodiment, the loop taker 42 oscillates back and forth in a rotarymovement as customary in the art.

A conventional feed dog 56 is provided under the bed, which carries outa known feed motion or moving into and out of the slot 55 of the needleplate 54 and advances a work fabric 93 on the work support in onedirection from said needle aperture 53 between each needle penetrationthereof. The feed dog 56 is secured to a feed bar 58 connected with afeed advancing shaft 57 which is swung by a forked rod 60 having twoforked end portions between which a feed cam 59 on the main shaft 24 isheld, thereby applying feed advance and return movements to the feed dog56. At the one end of the shaft 63 of a forked arm 62 connected to afeed lift eccentric 61 on said rock shaft 49 is provided an operable arm64 operably connected to said shaft 57, the feed dog 56 being applied upand down movements by the rotation of the eccentric 61.

It will be appreciated that as it is conventional in the art the linearwork-feeding mechanism is timed relatively to the needle reciprocationso that the feed dog 56 is lifted and advanced while the needle 30 israised out of any work on the needle plate 54, and the feed dog 56 islowered beneath the needle plates 54 and returned while the needledescends.

The chain stitch forming device of the present invention will bedescribed with reference to FIGS. 2-7. A chain stitch adapter member 67is placed into the loop taker 42 of assembly 36, rather than a bobbincase 43 and thread spool. At the center of the inner bottom surface ofthe loop taker 42 is a projecting bobbin supporting pin 66 (FIG. 3)having an annular groove 65 formed about the outer end portion. Thechain stitch member 67 comprises a forward plate like member 68 made ofa metal plate, at the upper end of which is disposed an upwardlyextending loop retaining projection 69 and a rear member 71 of plasticsmaterial secured to the forward member 68 by screws 70. The part of saidrear member 71 is formed as a contact element 74 which is engageable bythe inner edge of the curved overhanging lip 73 of front wall 72 of theloop taker 42; the lip portion 73 functions as a cam member; itsdistance from the center of rotation of loop taker 42 is variable, asseen in exaggerated form in FIGS. 8 and 10. That portion 75 of theforward member 68 which lies near its projection 69 freely engages withrecess 44 of the cover ring 38, preventing the chain stitch formingmember 47, like the bobbin case of the ordinary sewing machine, frombeing unduly rotated. At the center of the member 67 is formed a hole 76elongated in the vertical direction and having a prescribed width. Theinner surface of the upper surface of the upper end 77 of the hole isinclined as seen in FIG. 3 for the undermentioned purpose. Bobbinsupporting pin 66 is inserted into hole 76; since the hole is elongated,the chain stitch member 67 can reciprocate vertically. Numeral 78represents a substantially L-shaped stop lever adapted to engage ingroove 65 of pin 66. It is interposed between the forward and rearmembers 68 and 71, whose intermediate portion is rotatably pivoted by apivot 79 projectingly formed on said rear member 71. One end 80 of saidlever 78 is so disposed as to face the annular groove 65 of thebobbin-supporting pin 66. Numeral 81 denotes a first spring stretchedbetween the aforementioned end 80 of the lever 78 and the rear member71. This spring 81 urges said end 80 into the annular groove 65 of thebobbin-supporting pin 66 for engagement therewith, thereby preventingthe chain stitch forming member 67 from coming off the loop taker 42 andalso urging said member 67 upward so as to allow the contact member 74to be tightly attached to the curved overhanging lip 73 of the looptaker 42. A handgrip plate 82 is fitted to the front side of the forwardmember by a pin 83 swingably supported in the forward member 68. Anextension arm 85 is engageable with the other end 84 of the L-shapedlever 78 and another arm 87is engaged by a second spring 86. The gripplate 82 is normally depressed by the action of the second spring 86.When the grip plate 82 is raised against the force of springs 81 and 86,the arm member 85 engages with the other end 84 of the L-shaped lever 78and rotates it to remove end 80 thereof from the annular groove 65 ofthe bobbin-supporting pin 66. Numeral 88 (FIG. 7) denotes a bridgemember fixed to the loop taker housing 37 and numeral 89 (FIG. 2; FIG. astationary thread guide formed on said bridge member 88. This guide 89engages with the loop retaining projection 69 of the adapter 67 to allowthe loop 52 released from the loop taker 42 to be temporarily retainedby said projection 69, thereby obstructing the passage of the loop 52.The guide 89 is placed to be lower than the upper point reached by theloop retaining projection 69 for temporarily holding the loop of thethread 52 released from said loop taker 42 on projection 69. It preventsslipping out of the loop thread 52 by engagement with the projection 69.The curved overhanging lip 73 of the loop taker moves the adapter 67downwardly by engagement with contact element 74, thus constituting acam means and lowers the top of said projection 69 below the level ofsaid stationary thread guide 89 according to said oscillating movementof said loop taker 42 to permit formation of the loop bythread 52entrapped on said projection by the needle thread takeup mechanism afterthe needle upon being next lowered, has been passed through said loop.Numeral is a loop-restricting portion formed on the bridge member 88 ina manner to extend ahead of the loop retaining projection 48. When theloop released from the loop taker 42 is temporarily retained by the loopretaining projection 69, said loop-restricting portion 90 prevents saidloop 52, due to the lifting action of a thread take up mechanism, fromslipping over the upper surface of the loop-retaining projection 69 andgetting through the gap between said projection and stationary threadguide 89.

To employ the chain stitch forming device of the present in vention inan ordinary lock stitch sewing machine of FIG. 1, the bobbin case isremoved and the chain stitch member 67 is fitted instead into the looptaker 42. The grip plate 82 is raised against the force of springs 81,86 and the adapter 67 will then snap in place similar to the bobbincase.

Operation and formation of chain stitches: FIGS. 2 and 3 present thecondition where the loop 52 released from the loop taker 42 is lifted bythe thread takeup mechanism of FIG. 1, passes between the portion 75 ofthe forward member 68 lying near the projection 69 and the recess 44 ofthe loop taker 42 and is brought to rest at the upper part of theprojection 69 by the stationary thread guide 89. At this time, the looptends, due to the lifting action of the thread takeup mechanism, to slipover the upper surface of the projection 69 and get through the gapbetween said projection 69 and guide 89 (this tendency becomesparticularly prominent as the machine operation is more accelerated).However, the loop restriction portion 90 formed on the bridge member 88obstructs the loop in slipping over the upper surface of the projection69, thus preventing the omission of stitches.

After the aforementioned condition is realized, the work fabric 93 ismade to feed by the work-feeding mechanism for a distance equivalent toone stitch pitch. The needle 30 is brought down into the loop 52allowing the curved overhanging lip 73 of the loop taker 42 to engagewith the contact member 74. As a result of the rotary movement of looptaker 42, camming portion 73 engages member 74, and the chain stitchforming member 67 is urged downward against the force of the firstspring 81 therein. This downward urging is continued until theloop-retaining projection 69 disengages from the stationary threadedguide 89; movement of the adapter member 67 is guided by the elongatedhole 76 engaging with the bobbin supporting pin 66. Upon disengagementof projection 69 from guide 89, the loop 52 retained by said loopretaining projection 69 'is released. After the loop 52 is released, therear part of the upper end 77 of the elongated hole 76 engages with thebobbin supporting pin 66, so that the downward movement of the chainstitch forming member 67 is stopped. Rotation of the loop taker 42however, continues, and the contact member 74 continues to be engaged bythe curved overhanging camming lip 73 of the loop taker 42. As shown inFIG. 4, therefore the loop-retaining projection 69 of the chain stitchforming member 67 is inclined outwardly, that is, away from guide 89 andrestricted portion 90, thus separating from the released loop 52. Theinclined portion 77 on the inner surface of the upper end of theelongated hole 76 permits this tilting movement of member 67.

As the sewing machine keeps on running, a loop freshly formed by thedownward needle 30 is seized by the loop taker 42 in preparation for thefollowing stitch forming operation. At this time, and upon reverserotary movement of loop taker 42 and with it, camming lip 73, theloop-retaining projection 69 of the chain stitch member 47 is returnedfrom its inclined position conversely to the aforesaid case, allowingsaid member 67 to be lifted to its original level. Accordingly, when theloop retaining projection 69 is raised again, it is prevented from againseizing the released loop, causing no double stitches and permittinggood stitching at all times.

As shown in FIG. 7, a top portion 91 engaging with the upper end surfaceof the loop retaining projection 69 when it is lifted may be arranged onbridge member 88. Guide 89 and loop restricting portion 90 are formedinto a rectangular inverted C shape or channel in cross section andsurrounding projection 69, thereby defining a groove 92. According tothis arrangement, when the loop 52 released from the loop taker 42 istemporarily retained by the loop-retaining projection 69, the major partof the loop 52 is prevented by the loop-restricting portion 90 frompassing over the upper end surface of said projection 69. Even then theloop 52 tends to pass between said projection 69 and groove 92 and slipover the upper end surface of said projection 69. However, the topportion 91 of the aforesaid rectangular C shaped section fully retainsthe loop 52, and reliably prevents skipping of stitches. Manufacture ofthe stationary thread guide 89 and loop-restricting portion 90 togetherwith top portion 91 and the bridge member 88 is easily and cheaplyaccomplished.

Embodiment of FIGS. 8 to 11: the chain stitch forming device is adaptedfor use in a lock stitch sewing machine wherein the loop taker assembly(consisting of a loop taker housing, loop taker and bobbin caseretainer) is rotatable about a horizontal axis arranged perpendicularlyto the direction in which a work fabric travels over a needle plate. Thesame parts of this embodiment as those of the preceding one are denotedby the same numerals and description thereof is omitted. A chain stitchforming member 100 is fitted to a bobbin supporting pin 66 (FIGS. 8 and9) projecting at the center of the inner bottom surface of the looptaker 42. About the outermost end of said pin 66 is formed an annulargroove 65. The chain stitch member 100 is supported by pin 66 in amanner to move vertically through a vertically elongated hole 101 andanother elongated hole 102 having the same length as the former 101perforated by punching. Member 100 is prevented from moving inward by anembossed part 103 formed thereon so as to engage with the outermost endof the supporting pin 66. An upwardly extending loop retaining portion104 is formed on member 100. Member 100 is further formed with a contactstrip 105 closely attached under pressure to the inside of the curvedoverhanging lip 73 of the loop taker 42 which constitutes a cam memberfunctioning as in the preceding embodiment. The intermediate part 106located at the base of said loop-retaining projection 104 prevents,jointly with the recess 44 of the cover ring 38, the chain stitchforming member 100 from being unduly rotated, as is the case with thepreceding embodiment and an ordinary bobbin case. The loop retainingprojection 104 is formed to have a wide width in an opposite directionto the projection of the preceding embodiment, namely, in a directionperpendicular to that in which a work fabric 93 travels. The chainstitch forming member 100 has a stop lever 108 rotatably supported by apivot 107, the middle part essentially of said lever extending in adirection to face the annular groove 65 of the pin 66. A spring 109 isstretched between the other end of lever 108 and one side of the stitchforming member 100. Spring 109 causes the lever 104 to be fitted intothe annular groove 65 so as to prevent said lever 108 from coming offthe loop taker 42 of the chain stitch forming member 100 and urgesmember 100 upward to allow the contact strip 105 to be pressed to thecurved overhanging lip 73 of the loop taker 42. A hand-operable lever110 extends to the opposite side of the pivot 107 as an extension of thestop lever 108 in order to remove the stop lever 108 from the annulargroove 65. A stationary thread guide 11] is fonned at the underside ofthe needle plate 54. Stationary thread guide 11] engages with theloop-retaining projection 104 so as to allow the loop 52 released fromthe loop-seizing beak 41 of the loop taker 42 to be temporarily retainedby the loop-retaining projection 104, thereby preventing the loop 52from passing over projection 104.

A depression 112 is formed at that part of the needle plate which islocated around the needle eye when it is brought down, so as to ensurethe smooth run of the loop 52, when the thread is tightened. A strip 113is formed on the stop lever [08, which engages with the upper surface ofthe bobbin-supporting pin so as to prevent the chain stitch formingmember 100 from falling inwardly.

Operation: Essentially, the operation is similar to that previouslydescribed. When a work fabric 93 is moved forward for a distanceequivalent to one stitch pitch and the needle 30 is brought down againto the loop 52, the return rotation of the loop taker 42 causes thecurved overhanging camming lip 73 of said loop taker 42 to engage withthe contact strip 105, thereby urging the chain stitch forming memberdownward against the action of the spring 109. Downward urging iscontinued, the stitch forming member 100 is guided by the elongatedholes 101 and 102 engaging with the supporting pin 66, until theloop-retaining projection 104 is brought to a position where it isdisengaged from the stationary thread guide 1 l 1. At this time the loop52 retained by said projection 104 is released. Before it is urgeddownward to a position where it is disengaged from the guide 111, theloop-retaining projection 104 is pressed to the guide 111 under theaction of the curved overhanging lip 73 of the loop taker 42 as a resultof the return rotation of said loop taker 42.

FIGS. 10 and 11 show the condition where, upon completion of a returnoscillation, the loop taker 42 made a forward rotation and the loopseizing beak 41 took up a loop freshly formed by the descending needle30. The chain stitch forming member 100 is inclined in such a directionas to allow the loop-retaining projection 104 to be removed from thereleased loop 52 under the action of the curved overhanging lip 73 ofthe loop taker 42, namely, in a direction in which said member 100 iscarried away from the needle 30. Since the lip 73 of the loop taker 42frictionally contacts the contact strip 105, the inclination of thechain stitch forming member 100 is caused by the forward rotation ofsaid loop taker 42 in the same direction as the rotation. Of course,this inclination is carried out insofar as the intermediate portion 106of the loop retaining projection 104 is allowed to move crosswise in therecess 44. As the sewing machine further keeps on running, the chainstitch forming member 100 is lifted conversely to the just precedingoperation and brought back from the aforesaid inclined position.

in the second embodiment of the present invention, the stationary threadguide was formed on the underside of the needle plate, but the recess ofthe loop taker may be used as it is to serve as such stationary threadguide. However, the provision of a separate stop member is preferred toobtain tight stitches and in order to bring the needle reliably into theloop.

Like the preceding embodiment, that of FIGS. 8 and 11 offers greatconvenience, because chain stitches can bemade simply by fitting a chainstitch forming member into a loop taker assembly in place of the bobbincase of the ordinary lock stitch sewing machine. Double stitches areprevented and good chain stitches are formed. in addition, thisembodiment is of simpler arrangement than the first embodiment, becausea single spring serves the double purpose of allowing the stop lever tobe fitted into the annular groove of the bobbin supporting pin toprevent this lever from coming off the loop taker and urging the chainstitch member upward so as to cause the contact strip thereof to bepressed to the curved overhanging lip of the loop taker.

Embodiment of FIGS. 12 to 18: The same parts, particularly thoseassociated with the loop takeup assembly, of this third embodiment asthose of the preceding embodiments are denoted by the same numerals anddescription thereof is omitted.

A machine frame supports the rotary loop taker shaft of a loop takerassembly which can fully rotate about the central axis of said assembly.A loop taker 121 is fitted to the end of shaft 120. A bobbin caseretainer 122 containing a detachably fitted bobbin case of the knowntype is slidably retained in loop taker 121 which is so designed as tomake two full rotations during endwise reciprocation of the needle 30. Arecess 123 is formed at that part of the peripheral wall of the retainer122 which is located near the point of needle penetration. A restrainingmember 124 for the bobbin case retainer 122 is fitted to the machineframe, one end of said member 124 being fixed by screws 125' (FIG. 14).The upper end of restraining member 124 is formed with a projection 125freely engaging with the aforesaid recess 123 thereby allowing thebobbin case retainer 122 to be brought to rest. In this embodiment,similar to the other embodiments, the loop taker 121 and needle 30 aredriven in timed relationship with each other. A cylindrical case 128 isused in place of an ordinary bobbin case, at the central part of whichthere is projectingly disposed a short tube 129 for receiving thebobbin-supporting pin 126 projectingly provided at the central part ofthe inner bottom surface of the retainer 122 and having an annulargroove 127 at the top part. Cylindrical case 128 has a grip plate 130(FIG. 12) for allowing it to be detachably fitted into the retainer 122and has substantially the same shape and size as an ordinary bobbincase. The case has a projection 132 fitted in a recess 131 of saidbobbin case retainer 122. The short tube 129of the cylindrical case 128is inserted into a guide plate 133 (FIG. 18), which is securely set inplace within the cylindrical case 128 by a coil spring 134 and stop ring135..

A loop holder 136, perforated with a vertically elongated hole 137, isintroduced over the short tube 129, and placed to move verticallythrough the space defined by the guide plate 133 and the mutually facingfolded portions 138 formed on both sides of said guide plate 133. Theupper end of the loop holder 136 is notched to form a notch portion 140.The final projecting end forms a contact member 141, extending throughthe folded portions 138 formed in the guide plate 133 and those formedin the loop taker, and an upward projection 142 holding the loop. Anotch 143 is formed on the bottom wall of the recess 123 so as to allowthe projection 142, together with the cylinder case 128 to be detachablyfitted into the retainer 122. A spring 144 is stretched between theguide plate 133 and loop holder 136 so as to urge the loopretainingprojection 142 upward at all times. The aforementioned members denotedby numerals 128 to 144 constitute a chain stitch member to be detachablyfitted into a loop takeup assembly. A stationary thread guide 145 openat one end, is formed on the projection 125 of the restraining member124 (FIG. 15). Guide 145 engages the end of the upward projectionholding the loop by the action of the spring 144, thereby allowing theloop, when released from the loop-seizing beak 146 of loop taker 121 tobe retained by projection 142. A cam portion 147 is formed in the looptaker 121 so as to engage with the contact member 141 of the loop holder136 when the needle is brought down into a loop retained by the upwardprojection 142, thereby allowing the loop holder 136 to be brought downagainst the force of the spring 144 to release a loop from the loopretaining upward projection 142.

Operation: FIGS. 12 to 14 show the condition where the loop 52 releasedfrom the loop-seizing beak 146 of the loop taker 121 is lifted by athreaded takeup mechanism (not shown) and retained by the loop retainingupward projection 142 in cooperation with the guide 145 formed on theprojection 125 of the restraining member 124. After the aforesaidcondition is reached, a work fabric 93 is fed by one stitch pitch. Whenthe needle is brought down again into the loop 52 the cam portion 147(FIG. 15) formed on the loop taker 121 engages with the contact member141, as a result of the rotation of the loop taker 121, and urges loopholder 136 downward against the action of the spring 144, therebyreleasing the loop 52 retained by the loop-retaining upward projection142. As the sewing machine further keeps on running, the loop-seizingbeak 146 of the loop taker catches a loop, freshly formed by thedowncoming needle 30, in preparation for the formation of the followingchain stitch. At this time the contact member 141 is disengaged from thecam portion 147 to allow the loop retaining member 136 to be liftedagain by the action of the spring 144 and brought to a state ready toseize the loop 52 released from the loop taker.

In this third embodiment, the loop holder 136 is arranged to move withrespect to the stationary cylinder case 128. However, the chain stitchmember may be so arranged as to permit these members to move as anassembly.

As in the first and second embodiments, the chain stitch device of thethird embodiment is of simple arrangement and can be detachably fittedwith ease into an ordinary lock stitch sewing machine. The device of thethird embodiment particularly is simple in arrangement, so that it canbe easily manufactured at low cost.

What we claim is:

1. A chain stitch forming device for a lock stitch sewing machine, saidmachine including a frame having a work support formed with a needleaperture;

a thread-carrying eyed needle disposed above the work support forendwise reciprocation through said needle aperture;

a needle thread takeup mechanism mounted on said frame for alternatelytightening and loosening said needle thread in timed relationship withthe endwise reciprocation of said needle;

a loop taker disposed on said frame for circularly moving about the axisof the loop taker assembly, said loop taker being formed with abobbin-receiving cavity to accommodate a bobbin;

stop means for preventing the bobbin from making circular movementtogether with said loop taker,

means for driving said needle and loop taker in timed relationship insuch a manner that while said needle is being brought downwardly throughsaid needle aperture, the loop coming out of the needle eye is seized bysaid loop taker and that while said needle is being brought upwardly,the seized loop is released from said loop taker;

and a linear work-feeding mechanism for advancing said work fabriccarried on its support in a prescribed direction from said needleaperture during each endwise reciprocation of said needle;

wherein said chain stitch forming device comprises a body member formedto be fitted into the cavity of said loop taker in replacement of abobbin;

an upwardly projecting loop-retaining member disposed on said bodymember on the work-feeding side close to the point of needlepenetration;

means connected to said loop-retaining member to urge it upwardly;

a stationary thread guide interposed between said loopretaining memberand said point of needle penetration positioned at a point lower thanthe maximum height attained by the top of said loop-retaining member totemporarily retain the loop released from the loop taker on saidloop-retaining member by cooperation of said thread guide and saidloop-retaining member; and

cam means located between said loop taker and said loopretaining memberoperating in synchronism with the needle and engaging said loopretaining member to move the top of said loop-retaining member down tobelow the level of said stationary thread guide as a result of thecircular movement of said loop taker and to allow the loop retained onsaid loop-retaining member to be taken off therefrom by said threadtakeup mechanism after said needle, upon being brought down during asubsequent stitch-forming movement passes through said loop, therebyforming chain stitches with threads carried by said needle.

2. The chain stitch forming device for a lock stitch sewing machineaccording to claim 1 further comprising means for moving said top ofsaid loop-retaining member by the action of said cam means in suchdirection as to remove said top from said released loop after said topis brought down to below the level of said stationary thread guide.

3. The chain stitch forming device for a lock stitch sewing machineaccording to claim 1 wherein said stationary thread guide is positionedon the underside of said work support formed with said needle aperture.

4. The chain stitch fonning device for a lock stitch sewing machineaccording to claim I wherein said body member is formed t'o'fit thebobbin cavity and is of substantially the same shape and size as abobbin case to hold a bobbin when the machine is to make lock stitches,said body member being detachably fitted into the loop taker, and havinga movable grip plate disposed at the front of said body member toremovably lock said body member in position in the loop taker.

5. The chain stitch forming device for a lock stitch sewing machineaccording to claim 1 wherein the loop taker has a bobbin-supporting pinpositioned therein, the pin being formed with an annular groove at thefurthest end;

and said body member comprises a vertically elongated hole engaging withsaid bobbin-supporting pin so as to permit the vertical movement of saidupwardly projecting loopretaining member;

a stop lever having a base and an open end, the base being pivoted tosaid body member and the open end facing the annular groove of saidbobbin-supporting pin;

resilient means located between said stop lever and body member andurging said stop lever to engage with said annular groove, therebypreventing said body member from coming off said loop taker and alsourging said body member upwardly and manually operable means fordisengaging said stop lever from said annular groove against the actionof said resilient means.

6. The chain stitch forming device for a lock stitch sewing machineaccording to claim 5 wherein said elongated hole further has apredetermined width in the direction of said bobbin-supporting pin andan inclined upper end surface, said inclined upper end surface beingengageable by said cam means to shift the top of said loop-retainingmember to a point removed from the released loop after the top of saidloop retaining member is brought down to below the level of saidstationary threaded guide.

7. The chain stitch device for a lock stitch sewing machine according toclaim 5 wherein said manually operable means comprises a grip platefitted to said body member and located to rise or fall as required atthe front part of said body member in order to disengage said stop leverfrom said annular groove;

and a spring for normally keeping said grip plate in lowered state,thereby enabling said stop lever to be disengaged from said annulargroove when said grip plate is made to rise against the action of saidspring.

8. A chain stitch forming device for a lock stitch sewing machineincluding a frame having a work support formed with a needle aperture, aneedle with a thread carrying eye positioned above said support andcapable of making vertical reciprocations through the needle aperture, aneedle thread takeup mechanism disposed on the frame for alternatelytightening and loosening the needle thread in timed relationship withthe vertical reciprocations of the needle, a loop taker housing securedto said frame and having an internal circular raceway, a bobbin case, aloop taker having a discontinuous peripheral bearing rib journaled insaid raceway for oscillating movement around a horizontal axis andadapted to accommodate said bobbin case, a stop means for preventingsaid bobbin case from making oscillating movement together with saidloop taker, means for driving said needle and loop taker in prescribedtimed relationship in such a manner that while said needle is beingbrought downwardly through said needle aperture, the loop coming out ofsaid needle eye is seized by said loop taker and that while said needleis being brought upwardly, the seized loop is released from said looptaker, and a linear feeding mechanism of a work fabric held on itssupport member for advancing it in a prescribed direction from theneedle aperture during the reciprocations of said needle, said chainstitch forming device comprising a chain stitch forming member fittedinto said loop taker in replacement of said bobbin case, an upwardlyprojecting loop-retaining member mounted on said chain stitch formingmember in a manner to be located close to said needle aperture, meansshiftably mounting said loop-retaining member for movement between anupper loop-retaining position and a lower loop releasing position; 1

means normally biassing said loop retaining member into said upperloop-retaining position;

a stationary thread guide interposed between said loopretaining memberand said needle aperture at a point lower than a maximum height attainedby the top of said loop-retaining member so as to temporarily retain theloop on said loop-retaining member after being released from said looptaker, and cam means provided on said loop taker to engage the chainstitch forming device for a predetermined time during each stitch cycleto lower the top of said loop-retaining member below the level of saidstationary thread guide as a result of the oscillating movement of saidloop taker so as to allow the loop retained on said loop-retainingmember to be moved therefrom by the thread takeup mechanism after saidneedle passes through said loop on its next stitching cycle therebyforming chain stitches with threads carried by said needle.

9. The chain stitch forming device for a lock stitch sewing machineaccording to claim 8 wherein said cam means on the loop taker is formedon the curved overhanging lip of the front loop expanding wall thereof.

10. The chain stitch forming device for a lock stitch sewing machineaccording to claim 8 including a bridge member fitted on the loop takerhousing and the stationary thread guide formed in the bridge member.

11. The chain stitch forming device for a lock stitch sewing machineaccording to claim 10 wherein said bridge member is formed with aloop-restricting portion located close to said loop-retaining member toprevent the loop released from said loop taker, while being temporarilyretained by said loop retaining member, from passing over the top ofsaid loopretaining member due to the lifting action of said threadtakeup mechanism and being pulled through the space betweenloop-retaining member and the stationary thread guide.

12. A chain stitch forming device for a lock stitch sewing machineincluding a frame having a work support formed with a needle aperture, athread carrying eyed needle supported about the work support for endwisereciprocation through said needle aperture, a needle thread takeupmechanism mounted on said frame for alternately tightening and looseningsaid needle thread in timed relationship with the endwise reciprocationof said needle, a loop taker disposed on said frame rotatably about theaxis of the loop taker assembly, a bobbin case retainer supported insaid loop taker and adapted to accommodate a bobbin case, said bobbincase retainer being provided with a recess near said point of needlepenetration, a restraining member, the base of which is fixed to saidframe and the end of which has a projection freely engaging with saidrecess so as to prevent said bobbin case retainer from rotating togetherwith said loop taker, means for driving said needle and loop taker intimed relationship in such a manner that while said needle is beingbrought downwardly through said needle aperture, the loop coming out ofthe needle eye is seized by said loop taker and that while said needleis being brought upwardly, the seized loop is released from said looptaker, and a linear work-feeding mechanism for advancing said workfabric carried on its support in a prescribed direction from said needleaperture during each endwise reciprocation of said needle characterizedin that it further comprises a body member fitted into a bobbin caseretainer in replacement of said bobbin case, an upwardly projecting loopretaining member disposed on said body member on the workfeeding sideclose to the point of needle penetration, means connected to said loopretaining member so as to urge it upwardly, a stationary thread guideformed on the projection of said restraining member for temporarilyretaining the loop released from the loop taker on said loop-retainingmember in cooperation therewith and cam means formed on said loop takerengaging, and bringing the top of said loop retaining member down tobelow the level of said stationary thread machine according to claim 12wherein the stationary thread guide is open and formed in the projectionof said restraining member, the bottom plane of said guide beingpositioned lower than a maximum height attained by the top of said loopretaining member.

1. A chain stitch forming device for a lock stitch sewing machine, saidmachine including a frame having a work support formed with a needleaperture; a thread-carrying eyed needle disposed above the work supportfor endwise reciprocation through said needle aperture; a needle threadtakeup mechanism mounted on said frame for alternately tightening andloosening said needle thread in timed relationship with the endwisereciprocation of said needle; a loop taker disposed on said frame forcircularly moving about the axis of the loop taker assembly, said looptaker being formed with a bobbin-receiving cavity to accommodate abobbin; stop means for preventing the bobbin from making circularmovement together with said loop taker, means for driving said needleand loop taker in timed relationship in such a manner that while saidneedle is being brought downwardly through said needle aperture, theloop coming out of the needle eye is seized by said loop taker and thatwhile said needle is being brought upwardly, the seized loop is releasedfrom said loop taker; and a linear work-feeding mechanism for advancingsaid work fabric carried on its support in a prescribed direction fromsaid needle aperture during each endwise reciprocation of said needle;wherein said chain stitch forming device comprises a body member formedto be fitted into the cavity of said loop taker in replacement of abobbin; an upwardly projecting loop-retaining member disposed on saidbody member on the work-feeding side close to the point of needlepenetration; means connected to said loop-retaining member to urge itupwardly; a stationary thread guide interposed between saidloop-retaining member and said point of needle penetration positioned ata point lower than the maximum height attained by the top of saidloop-retaining member to temporarily retain the loop released from theloop taker on said loop-retaining member by cooperation of said threadguide and said loop-retaining member; and cam means located between saidloop taker and said loopretaining member operating in synchronism withthe needle and engaging said loop retaining member to move the top ofsaid loop-retaining member down to below the level of said stationarythread guide as a result of the circular movement of said loop taker andto allow the loop retained on said loopretaining member to be taken offtherefrom by said thread takeup mechanism after said needle, upon beingbrought down during a subsequent stitch-forming movement passes throughsaid loop, thereby forming chain stitches with threads carried by saidneedle.
 2. The chain stitch forming device for a lock stitch sewingmachine according to claim 1 further comprising means for moving saidtop of said loop-retaining member by the action of said cam means insuch direction as to remove said top from said released loop after saidtop is brought down to below the level of said stationary thread guide.3. The chain stitch forming device for a lock stitch sewing machineaccording to claim 1 wherein said stationary thread guide is positionedon the underside of said work support formed with said needle aperture.4. The chain stitch forming device for a lock stitch sewing machineaccording to claim 1 wherein said body member is formed to fit thebobbin cavity and is of substantially the same shape and size as abobbin case to hold a bobbin when the machine is to make lock stitches,said body member being detachably fitted into the loop taker, and havinga movable grip plate disposed at the front of said body member toremovably lock said body member in position in the loop taker.
 5. Thechain stitch forming device for a lock stitch sewing machine accordingto claim 1 wherein the loop taker has a bobbin-supporting pin positionedtherein, the pin being formed with an annular groove at the furthestend; and said body member comprises a vertically elongated hole engagingwith said bobbin-supporting pin so as to permit the vertical movement ofsaid upwardly projecting loop-retaining member; a stop lever having abase and an open end, the base being pivoted to said body member and theopen end facing the annular groove of said bobbin-supporting pin;resilient means located between said stop lever and body member andurging said stop lever to engage with said annUlar groove, therebypreventing said body member from coming off said loop taker and alsourging said body member upwardly and manually operable means fordisengaging said stop lever from said annular groove against the actionof said resilient means.
 6. The chain stitch forming device for a lockstitch sewing machine according to claim 5 wherein said elongated holefurther has a predetermined width in the direction of saidbobbin-supporting pin and an inclined upper end surface, said inclinedupper end surface being engageable by said cam means to shift the top ofsaid loop-retaining member to a point removed from the released loopafter the top of said loop retaining member is brought down to below thelevel of said stationary thread guide.
 7. The chain stitch device for alock stitch sewing machine according to claim 5 wherein said manuallyoperable means comprises a grip plate fitted to said body member andlocated to rise or fall as required at the front part of said bodymember in order to disengage said stop lever from said annular groove;and a spring for normally keeping said grip plate in lowered state,thereby enabling said stop lever to be disengaged from said annulargroove when said grip plate is made to rise against the action of saidspring.
 8. A chain stitch forming device for a lock stitch sewingmachine including a frame having a work support formed with a needleaperture, a needle with a thread carrying eye positioned above saidsupport and capable of making vertical reciprocations through the needleaperture, a needle thread takeup mechanism disposed on the frame foralternately tightening and loosening the needle thread in timedrelationship with the vertical reciprocations of the needle, a looptaker housing secured to said frame and having an internal circularraceway, a bobbin case, a loop taker having a discontinuous peripheralbearing rib journaled in said raceway for oscillating movement around ahorizontal axis and adapted to accommodate said bobbin case, a stopmeans for preventing said bobbin case from making oscillating movementtogether with said loop taker, means for driving said needle and looptaker in prescribed timed relationship in such a manner that while saidneedle is being brought downwardly through said needle aperture, theloop coming out of said needle eye is seized by said loop taker and thatwhile said needle is being brought upwardly, the seized loop is releasedfrom said loop taker, and a linear feeding mechanism of a work fabricheld on its support member for advancing it in a prescribed directionfrom the needle aperture during the reciprocations of said needle, saidchain stitch forming device comprising a chain stitch forming memberfitted into said loop taker in replacement of said bobbin case, anupwardly projecting loop-retaining member mounted on said chain stitchforming member in a manner to be located close to said needle aperture,means shiftably mounting said loop-retaining member for movement betweenan upper loop-retaining position and a lower loop releasing position;means normally biassing said loop retaining member into said upperloop-retaining position; a stationary thread guide interposed betweensaid loop-retaining member and said needle aperture at a point lowerthan a maximum height attained by the top of said loop-retaining memberso as to temporarily retain the loop on said loop-retaining member afterbeing released from said loop taker, and cam means provided on said looptaker to engage the chain stitch forming device for a predetermined timeduring each stitch cycle to lower the top of said loop-retaining memberbelow the level of said stationary thread guide as a result of theoscillating movement of said loop taker so as to allow the loop retainedon said loop-retaining member to be moved therefrom by the thread takeupmechanism after said needle passes through said loop on its nextstitching cycle thereby forming chain stitches with threads carried bysaid needle.
 9. ThE chain stitch forming device for a lock stitch sewingmachine according to claim 8 wherein said cam means on the loop taker isformed on the curved overhanging lip of the front loop expanding wallthereof.
 10. The chain stitch forming device for a lock stitch sewingmachine according to claim 8 including a bridge member fitted on theloop taker housing and the stationary thread guide formed in the bridgemember.
 11. The chain stitch forming device for a lock stitch sewingmachine according to claim 10 wherein said bridge member is formed witha loop-restricting portion located close to said loop-retaining memberto prevent the loop released from said loop taker, while beingtemporarily retained by said loop retaining member, from passing overthe top of said loop-retaining member due to the lifting action of saidthread takeup mechanism and being pulled through the space betweenloop-retaining member and the stationary thread guide.
 12. A chainstitch forming device for a lock stitch sewing machine including a framehaving a work support formed with a needle aperture, a thread carryingeyed needle supported about the work support for endwise reciprocationthrough said needle aperture, a needle thread takeup mechanism mountedon said frame for alternately tightening and loosening said needlethread in timed relationship with the endwise reciprocation of saidneedle, a loop taker disposed on said frame rotatably about the axis ofthe loop taker assembly, a bobbin case retainer supported in said looptaker and adapted to accommodate a bobbin case, said bobbin caseretainer being provided with a recess near said point of needlepenetration, a restraining member, the base of which is fixed to saidframe and the end of which has a projection freely engaging with saidrecess so as to prevent said bobbin case retainer from rotating togetherwith said loop taker, means for driving said needle and loop taker intimed relationship in such a manner that while said needle is beingbrought downwardly through said needle aperture, the loop coming out ofthe needle eye is seized by said loop taker and that while said needleis being brought upwardly, the seized loop is released from said looptaker, and a linear work-feeding mechanism for advancing said workfabric carried on its support in a prescribed direction from said needleaperture during each endwise reciprocation of said needle characterizedin that it further comprises a body member fitted into a bobbin caseretainer in replacement of said bobbin case, an upwardly projecting loopretaining member disposed on said body member on the work-feeding sideclose to the point of needle penetration, means connected to said loopretaining member so as to urge it upwardly, a stationary thread guideformed on the projection of said restraining member for temporarilyretaining the loop released from the loop taker on said loop-retainingmember in cooperation therewith and cam means formed on said loop takerengaging, and bringing the top of said loop retaining member down tobelow the level of said stationary thread guide as a result of rotarymovement of said loop taker so as to allow the loop retained on saidloop-retaining member to be taken off therefrom by said needle threadtakeup means after the needle being brought down next time passesthrough said loop, thereby forming chain stitches with threads carriedby said needle.
 13. The lock stitch forming device for a lock stitchsewing machine according to claim 12 wherein the stationary thread guideis open and formed in the projection of said restraining member, thebottom plane of said guide being positioned lower than a maximum heightattained by the top of said loop retaining member.